Enable SMTP Authentication in Outlook Print
If you are able to access emails from the webmail program such as Horde / Squirrel mail, you can be assured that the mail server is working normally. 
However, if you are unable to send out emails using Microsoft Outlook / Outlook Express [no problem receiving], please make sure you do the following:

>> Enable SMTP Auth [Authentication] in Outlook

Microsoft Outlook Settings:

Go to "Tools [at the top], >> Email Accounts >> Next [view or change...] >> Change.. >> More Settings.. >> Outgoing server"

Email Accounts Settings

Advanced Email Settings

*Outlook Express not illustrated here

Resources: http://en.wikipedia.org/wiki/SMTP-AUTH


Below is an example of the error log :

Quote:
[129.7.190.67]:2234 is currently not permitted to relay through this server. Perhaps you have not logged into the pop/imap server in the last 30 minutes or do not have SMTP Authentication turned on in your email client.
 
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